Microbes not creating 'dead zones' in Gulf

by Seth Borenstein - Sept. 8, 2010 12:00 AMAssociated Press

WASHINGTON - Federal scientists are reporting the best possible scenario for BP's leaked oil: Microbes are munching the underwater oil, but not robbing the Gulf of Mexico of much-needed oxygen or creating so-called dead zones.

Oxygen levels in some places where the BP oil spilled are down by 20 percent, but that's not nearly low enough to create dead zones where fish can't live, according to a 95-page report released Tuesday.

In an unusual move, BP released 771,000 gallons of chemical dispersant at the leaking wellhead, about a mile deep, instead of just on the water surface to break up the oil into tiny droplets.

That makes it easier for the oil-eating microbes to do their job, but in doing so they deplete the water of oxygen at places. Scientists were hoping that the oil was degrading but not at a rate that would cause lack of oxygen problems.

"Has it hit the sweet spot? Yes. Was it by design? Partly," said Steve Murawski, the National Oceanic and Atmospheric Administration senior scientist who headed the federal team.

Oxygen levels would have had to drop an additional 70 percent to be classified as dead zones, he said.

The Gulf already has a yearly major problem with a natural dead zone - the size of Massachusetts this year - because of farm runoff coming down the Mississippi River.

Federal officials had been tracking oxygen levels and use of chemical dispersants since the oil spill. Had the oxygen plummeted near dangerous levels, the dispersant use would have been stopped.